Field of the Invention
The present invention relates to a honeycomb structure, and more particularly, it relates to a honeycomb structure in which it is possible to decrease a thickness of a circumferential coating layer but it is possible that the circumferential coating layer is hard to be damaged.
Description of the Related Art
In recent years, consciousness for environmental problems has increased in the community as a whole, and in a technical field in which fuel is burnt to generate power, various technologies have been developed to remove toxic components such as nitrogen oxides from an exhaust gas generated during the burning of the fuel.
Heretofore, for a purifying treatment of toxic substances such as HC, CO and NOx contained in the exhaust gas emitted from a car engine or the like, a honeycomb structure onto which a catalyst is loaded has been used. Furthermore, the honeycomb structure, in which open ends of cells defined by porous partition walls are plugged, has also been used as an exhaust gas purifying filter.
The honeycomb structure is a pillar-shaped structure having partition walls defining a plurality of cells which become through channels for the exhaust gas. Such a honeycomb structure includes, in its circumferential portion, a circumferential wall which covers the pillar-shaped structure. As the circumferential wall of the honeycomb structure, there are, for example, roughly two types of circumferential walls as follows.
The first type of circumferential wall is a circumferential wall formed integrally with the partition walls when forming the partition walls. As described above, the circumferential wall formed integrally with the partition walls is usually often referred to as the circumferential wall. The second type of circumferential wall is a circumferential wall formed by coating a circumferential portion of the honeycomb structure with a coating material or the like, and drying the applied coating material, followed by firing when necessary. This circumferential wall is usually often referred to as a circumferential coating layer. For example, there is disclosed a honeycomb structure including a honeycomb segment bonded body in which bonding surfaces of a plurality of honeycomb segments are integrally bonded to one another via a bonding layer, and the circumferential coating layer which coats a circumferential surface of the honeycomb segment bonded body (e.g., see Patent Document 1).                [Patent Document 1] JP-A-2007-14886        